U.S. patent number 10,840,192 [Application Number 15/481,275] was granted by the patent office on 2020-11-17 for stacked silicon package assembly having enhanced stiffener.
This patent grant is currently assigned to XILINX, INC.. The grantee listed for this patent is Xilinx, Inc.. Invention is credited to Raghunandan Chaware, Ganesh Hariharan, Shin S. Low, Inderjit Singh, Nael Zohni.
United States Patent |
10,840,192 |
Zohni , et al. |
November 17, 2020 |
Stacked silicon package assembly having enhanced stiffener
Abstract
A chip package assembly and method for fabricating the same are
provided which utilize a stiffener to improve a package substrate
against out of plane deformation. In one example, a chip package
assembly is provided that includes a package substrate, at least
one integrated circuit (IC) die and a stiffener. The package
substrate has a first surface and a second surface coupled by a
side wall. The at least one IC die is disposed on the first surface
of the package substrate. The stiffener is disposed outward of the
at least one IC die. The stiffener has a first surface disposed
outward of and bonded to the side wall of the package substrate.
The stiffener has a second surface bonded to at least one of the
first and second surfaces of the package substrate.
Inventors: |
Zohni; Nael (San Jose, CA),
Low; Shin S. (Cupertino, CA), Singh; Inderjit (Saratoga,
CA), Chaware; Raghunandan (Sunnyvale, CA), Hariharan;
Ganesh (Santa Clara, CA) |
Applicant: |
Name |
City |
State |
Country |
Type |
Xilinx, Inc. |
San Jose |
CA |
US |
|
|
Assignee: |
XILINX, INC. (San Jose,
CA)
|
Family
ID: |
1000002569466 |
Appl.
No.: |
15/481,275 |
Filed: |
April 6, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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14990560 |
Jan 7, 2016 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L
21/4817 (20130101); H01L 23/04 (20130101); H01L
21/52 (20130101); H01L 24/14 (20130101); H01L
21/54 (20130101); H01L 23/562 (20130101); H01L
2224/1412 (20130101); H01L 2224/145 (20130101) |
Current International
Class: |
H01L
21/52 (20060101); H01L 21/54 (20060101); H01L
23/04 (20060101); H01L 21/48 (20060101); H01L
23/00 (20060101) |
Field of
Search: |
;257/712-713,E23.08-E23.113 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2001135937 |
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May 2001 |
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JP |
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2001196487 |
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Jul 2001 |
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JP |
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2003068931 |
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Mar 2003 |
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JP |
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2003100924 |
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Apr 2003 |
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JP |
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2005159136 |
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Jun 2005 |
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JP |
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2005159136 |
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Jun 2005 |
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JP |
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2006196857 |
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Jul 2006 |
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JP |
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2010192653 |
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Sep 2010 |
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JP |
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Other References
Specification and drawings for U.S. Appl. No. 14/990,560, filed
Jan. 7, 2016. cited by applicant.
|
Primary Examiner: Ho; Hoang-Quan
Attorney, Agent or Firm: Patterson + Sheridan, LLP
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
This Application is a divisional of U.S. application Ser. No.
14/990,560, filed Jan. 7, 2016, which is incorporated herein by
reference in its entirety.
Claims
What is claimed is:
1. A chip package assembly, comprising: a package substrate having
a first surface and a second surface coupled by a side wall; at
least one integrated circuit (IC) die disposed on the first surface
of the package substrate; a stiffener having a first surface
disposed outward of and bonded to the side wall of the package
substrate, the stiffener having a second surface bonded to at least
one of the first and second surfaces of the package substrate, the
stiffener circumscribing the IC die, the stiffener including a
third surface disposed opposite the first surface of the stiffener
and parallel thereto; an adapter, not integral with the package
substrate and the stiffener, coupled to the stiffener, the adapter
including an outer wall substantially aligned with the third
surface of the stiffener; and a plurality of solder balls disposed
on the second surface of the package substrate.
2. The chip package assembly of claim 1, wherein the stiffener is
bonded to the adapter and the first surface of the package
substrate.
3. The chip package assembly of claim 1, wherein the stiffener is
bonded to the adapter and the second surface of the package
substrate.
4. The chip package assembly of claim 1, wherein the stiffener
further comprises: a standoff portion projecting below the second
surface of the package substrate.
5. The chip package assembly of claim 4, wherein the solder balls
extend a distance from the second surface of the package substrate
beyond the standoff portion.
6. The chip package assembly of claim 1, further comprising: a lid
coupled to the stiffener and extending across the IC die.
7. The chip package assembly of claim 6, wherein the stiffener is
bonded to the first surface of the package substrate and to the
lid.
8. The chip package assembly of claim 6, wherein the stiffener is
bonded to the second surface of the package substrate and to the
lid.
9. The chip package assembly of claim 6, wherein the stiffener
further comprises: a standoff portion projecting below the second
surface of the package substrate.
10. The chip package assembly of claim 9, wherein the solder balls
extend a distance from the second surface of the package substrate
beyond the standoff portion.
11. The chip package assembly of claim 1, wherein the stiffener is
bonded to the side wall and the second surface of the package
substrate.
12. A chip package assembly comprising: a package substrate having
a first surface and a second surface coupled by a side wall; at
least one integrated circuit (IC) die disposed on the first surface
of the package substrate; a stiffener circumscribing the IC die and
having: a first surface disposed outward of and bonded to the side
wall of the package substrate; a second surface bonded to at least
one of the first and second surfaces of the package substrate and
including: a first portion covering a first corner of the package
substrate; and a second portion covering a second corner of the
package substrate, wherein the second surface of the stiffener is
discontinuous between the first and second portions; and a third
surface disposed opposite the first surface of the stiffener and
parallel thereto; and an adapter, not integral with the package
substrate and the stiffener, coupled to the stiffener, the adapter
including an outer wall substantially aligned with the third
surface of the stiffener.
13. The chip package assembly of claim 1, wherein the second
surface of the stiffener covers only a portion of the first surface
or the second surface of the package substrate.
14. The chip package assembly of claim 1, wherein the stiffener
comprises: a plurality of stiffener segments, each segment bonded
to a different portion of the package substrate.
15. The chip package assembly of claim 1, wherein a material of the
adapter and a material of the stiffener are the same.
16. The chip package assembly of claim 1, wherein the adapter is
bonded to the stiffener.
17. The chip package assembly of claim 1, wherein the adapter is
mechanically coupled to the stiffener.
18. The chip package assembly of claim 1, wherein the adapter
includes a top wall, a bottom wall parallel to the top wall, an
inner wall perpendicular to the top wall, the outer wall parallel
to the inner wall, an outer mounting surface parallel to the inner
wall, and a bottom mounting surface parallel to the top wall, and
wherein at least one of the outer mounting surface and the bottom
mounting surface is bonded to the stiffener.
19. The chip package assembly of claim 1, wherein the adapter
includes a top wall, a bottom wall parallel to the top wall, an
inner wall perpendicular to the top wall, an outer wall parallel to
the inner wall, an inner mounting surface parallel to the outer
wall, and a bottom mounting surface parallel to the top wall, and
wherein at least one of the inner mounting surface and the bottom
mounting surface is bonded to the stiffener.
20. The chip package assembly of claim 19, wherein the outer wall
of the adapter is spaced apart from the stiffener by a length of
the bottom wall.
21. A chip package assembly, comprising: a package substrate having
a first surface and a second surface coupled by a side wall; at
least one integrated circuit (IC) die disposed on the first surface
of the package substrate; a stiffener circumscribing the IC die and
having: a first surface disposed outward of and bonded to the side
wall of the package substrate; a second surface bonded to at least
one of the first and second surfaces of the package substrate; a
third surface disposed opposite the first surface of the stiffener
and parallel thereto; and a standoff portion projecting below the
second surface of the package substrate; and an adapter, not
integral with the package substrate and the stiffener, coupled to
the stiffener, the adapter including an outer wall substantially
aligned with the third surface of the stiffener.
Description
TECHNICAL FIELD
Embodiments of the present invention generally relate to a chip
package assembly, and in particular, to chip package assembly
comprising at least one integrated circuit (IC) die and stiffener
disposed on a package substrate, the stiffener stiffening the
package substrate against out of plane deformation.
BACKGROUND
Electronic devices, such as tablets, computers, copiers, digital
cameras, smart phones, control systems and automated teller
machines, among others, often employ electronic components which
leverage chip package assemblies for increased functionality and
higher component density. Conventional chip packaging schemes often
utilize a package substrate, often in conjunction with a
through-silicon-via (TSV) interposer, to enable a plurality of
integrated circuit (IC) dice to be mounted to a single package
substrate. The IC dice may include memory, logic or other IC
devices.
Out of plane deformation of the package substrate can be
problematic to conventional chip packaging schemes. In many
instances, a stiffener is utilized to stiffening the package
substrate against out of plane deformation. However, particularly
in larger chip package assemblies, the stiffener itself may bend or
twist, or even become delaminated from package substrate, thus
still permitting undesirable warpage and bending during manufacture
and/or use. Such warpage and bending of the package substrate can
lead to solder connection failure or other damage to the components
and devices of the chip package assembly, which may detrimentally
effect device performance and reliability.
Therefore, a need exists for an improved chip package assembly, and
in particular, to a chip package assembly having an improved
stiffener.
SUMMARY
A chip package assembly and method for fabricating the same are
provided which utilize a stiffener to improve a package substrate
against out of plane deformation. In one example, a chip package
assembly is provided that includes a package substrate, at least
one integrated circuit (IC) die and a stiffener. The package
substrate has a first surface and a second surface coupled by a
side wall. The at least one IC die is disposed on the first surface
of the package substrate. The stiffener is disposed outward of the
at least one IC die. The stiffener has a first surface disposed
outward of and bonded to the side wall of the package substrate.
The stiffener has a second surface bonded to at least one of the
first and second surfaces of the package substrate
In another example, a method for fabricating a chip package
assembly is provided that includes attaching a stiffener to a
package substrate prior to attaching one or more IC dice to the
package substrate.
BRIEF DESCRIPTION OF THE DRAWINGS
So that the manner in which the above recited features of the
present invention can be understood in detail, a more particular
description of the invention, briefly summarized above, may be had
by reference to embodiments, some of which are illustrated in the
appended drawings. It is to be noted, however, that the appended
drawings illustrate only typical embodiments of this invention and
are therefore not to be considered limiting of its scope, for the
invention may admit to other equally effective embodiments.
FIGS. 1-4 are a cross sectional schematic views of integrated chip
package assemblies, each including at least one integrated circuit
(IC) die and stiffener disposed on a package substrate.
FIG. 5 is a partial sectional view of an alternative example of a
stiffener which may be utilized in an integrated chip package
assembly, such as the integrated chip package assemblies of FIGS.
1-4.
FIGS. 6-8 and 11 are top views stiffeners that may be utilized in
an integrated chip package assembly, such as the integrated chip
package assemblies of FIGS. 1-4.
FIGS. 9-10 are sectional views of the stiffener of FIG. 8 taken
respectively along section lines 9-9 and 10-10.
FIGS. 12-13 are partial sectional views of a stiffener with adapter
that may be utilized in an integrated chip package assembly, such
as the integrated chip package assemblies of FIGS. 1-4.
FIG. 14 is a block diagram of one example of a method for forming a
chip package assembly having improved stiffener.
FIG. 15 is a block diagram of another example of a method for
forming a chip package assembly having improved stiffener.
To facilitate understanding, identical reference numerals have been
used, where possible, to designate identical elements that are
common to the figures. It is contemplated that elements of one
embodiment may be beneficially incorporated in other
embodiments.
DETAILED DESCRIPTION
A chip package assembly and method for fabricating the same are
provided which utilize an improved stiffener. The chip package
assembly described herein includes at least one integrated circuit
(IC) die and stiffener disposed on a package substrate. The
stiffener is configured to increase the resistance of the package
substrate to out of plane deformation during the fabrication and
use of the chip package assembly. Advantageously, the enhanced
stiffness of the chip package assembly improves reliability and
performance. In various examples described herein one or more
advantages may be realized that include stiffening the package
substrate both the horizontal and vertical axis, greater area for
adhesive attach for reduced delamination, more space for surface
mounted circuit elements, such as chip capacitors, thinner package
profile and ball grid array (BGA) stand-off height control, among
other benefits.
Turning now to FIG. 1, an exemplary integrated chip package
assembly 100 is schematically illustrated. The chip package
assembly 100 includes at least one or more IC dice 114 connected
optionally by a silicon-through-via (TSV) interposer 112 to a
package substrate 122. Although two IC dice 114 are shown in FIG.
1, the number of IC dice may range from one to as many as can be
fit within the chip package assembly 100. In some implementations,
the interposer 112 may be omitted with the one or more IC dice 114
connected directly to a top surface 102 of the package substrate
122. A stiffener 154 is coupled to at least one side wall 106 of
the package substrate 122 in a manner that enhances the resistance
of the package substrate 122 against out of plane deformation, as
further discussed below.
The interposer 112, when present, includes circuitry for
electrically connecting the dice 114 to circuitry of the package
substrate 122. The circuitry of the interposer 112 may optionally
include transistors and/or other circuit elements. Package bumps
120, also known as "C4 bumps," are utilized to provide an
electrical connection between the circuitry of the interposer 112
and the circuitry of the package substrate 122. A bottom surface
104 of the package substrate 122 may be mounted and connected to a
top surface 108 of a printed circuit board (PCB) 136, utilizing
solder balls 134, wire bonding or other suitable technique. An
undermolding 144 may be utilized to fill the space not taken by the
package bumps 120 between the PCB 136 and the interposer 112.
The IC dice 114 are mounted to one or more surfaces of the
interposer 112, or alternatively in implementations wherein an
interposer is not utilized, to the package substrate 122. The IC
dice 114 may be programmable logic devices, such as field
programmable gate arrays (FPGA), memory devices, optical devices,
processors or other IC logic structures. Optical devices include
photo-detectors, lasers, optical sources, and the like. In the
example depicted in FIG. 1, the IC dice 114 are mounted to a top
surface of the interposer 112 by a plurality of micro-bumps 118.
The micro-bumps 118 electrically connect the circuitry of each IC
die 114 to circuitry of the interposer 112. The circuitry of the
interposer 112 connects the micro-bumps 118 to selective package
bumps 120, and hence, connects selective circuitry of each IC die
114 to the package substrate 122, to enable communication of the
dice 114 with the PCB 136 after the chip package assembly 100 is
mounted within an electronic device (not shown). When the optional
interposer 112 is not present, the micro-bumps 118 connects
selective circuitry of each IC die 114 to the package substrate 122
to enable communication of the dice 114 with the PCB 136. An
undermolding 142 may be utilized to fill the space not taken by the
micro-bumps 118 between the dice 114 and interposer 112.
An optional lid 150 (shown in phantom) is disposed over the dice
114. In some implementations, the lid 150 may be fabricated from a
plastic material or other suitable material. In other
implementations particularly where it is desirable to utilize the
lid 150 to receive heat from the dice 114, the lid 150 may be
fabricated from a thermally conductive material, such as copper,
nickel-plated copper or aluminum, among other suitable materials.
The lid 150 may have a thickness of between about 0.5 mm and about
3.0 mm, although other thicknesses may be utilized. A heat sink,
not shown, may optionally be mounted to the lid 150.
The lid 150 may be coupled to the stiffener 154 to increase the
rigidity of the chip package assembly 100. For example, the lid 150
may be coupled to the stiffener 154 by an adhesive (not shown),
such as an epoxy.
An adhesive 140 may also be utilized to couple the lid 150 to the
dice 114. The adhesive 140 may be selected to provide a thermally
conductive path between the lid 150 to the dice 114 so that heat
generated by the dice 114 may be dissipated through the lid 150.
The adhesive 140 may be a soft or compliant adhesive to allow
compensation between mismatched heights of neighboring dice 114
within the chip package assembly 100. In one example, the adhesive
140 may be a thermal gel or thermal epoxy, such as for example,
packaging component attach adhesives available from AI Technology,
Inc., located in Princeton Junction, N.J.
The stiffener 154 is coupled to the package substrate 122 outward
the IC dice 114. The stiffener 154 extends beyond the side walls
106 of the package substrate 122 to provide mechanical support that
helps prevent the chip package assembly 100 from bowing and
twisting. The stiffener 154 may be a single layer structure or a
multi-layer structure. The stiffener 154 may be a single one-piece
structure or a multi-piece structure. The stiffener 154 may
circumscribe the package substrate 122 as a single structure, or
multiple connected or unconnected structures may be used. Although
the stiffener 154 is only shown in sectional profile in FIG. 1, the
stiffener 154 may have a closed ring shape, an open ring shape, or
other shape suitable for increasing the rigidity of the package
substrate 122.
The stiffener 154 may be made of ceramic, metal or other various
inorganic materials, such as aluminum oxide (Al.sub.2O.sub.3),
aluminum nitride (AlN), silicon nitride (SiN), silicon (Si), copper
(Cu), aluminum (Al), and stainless steel, among other materials.
The stiffener 154 can also be made of organic materials such as
copper-clad laminate.
The stiffener 154 generally includes an inner wall 156 coupled to
an outer wall 152 by a top wall 164. The stiffener 154 also
includes a bottom wall 162 disposed at the opposite end of the
stiffener 154 relative to the top wall 164. The bottom wall 162 is
coupled at least to the outer wall 152.
The stiffener 154 includes a side mounting surface 160 and a bottom
mounting surface 158 at the interface between the inner wall 156
and the bottom wall 162. In one example, the side mounting surface
160 is generally perpendicular to the planar orientation of the
package substrate 122, and may be perpendicular to one or both of
the top and bottom walls 164, 162. Similarly, the bottom mounting
surface 158 is generally parallel to the planar orientation of the
package substrate 122, and may be parallel to one or both of the
top and bottom walls 164, 162. The side mounting surface 160 may
extend from the inner wall 156 and intersect with the bottom
mounting surface 158, with the bottom mounting surface 158 then
extending to the bottom wall 162. The mounting surfaces 158, 160
also disrupt the generally rectangular profile of the stiffener
154, thereby increasing the rigidity of the stiffener 154.
Additionally, as the bottom mounting surface 158 is only a fraction
of the width between the inner and outer walls 156, 152 of the
stiffener 154, the inner wall 156 is closer to the side wall 106 of
the package substrate 122, thereby result in greater area of the
top surface 102 of the package substrate 122 being exposed inward
of the stiffener 154 as compared to conventional chip package
assemblies. The greater top surface area of the package substrate
122 increases the area available to accommodate the IC dice 114 and
surface mounted components, such as diodes, capacitors, resistors
and the like.
The mounting surfaces 158, 160 are configured contact and secure
the stiffener 154 to the package substrate 122. In one example, the
bottom mounting surface 158 contacts and is bonded to the top
surface 102 of the package substrate 122. The bottom mounting
surface 158 may be bonded to the top surface 102 of the package
substrate 122 utilizing an epoxy or other suitable adhesive.
Examples of suitable adhesives for bonding the bottom mounting
surface 158 to the top surface 102 include Henkel MC-723, Dow
Corning SE-4450, and Shin-Etsu 9080S-1, among others.
Similarly, the side mounting surface 160 contacts and is bonded to
the side wall 106 of the package substrate 122. The side mounting
surface 160 may be bonded to the side wall 106 of the package
substrate 122 utilizing an epoxy or other adhesive suitable for
bonding the bottom mounting surface 158. Alternatively, one or both
of the mounting surfaces 158, 160 may be secured to the package
substrate 122 utilizing a mechanical technique, such as staking,
snap fit, press fit, fastening or other suitable technique.
As the stiffener 154 is coupled to the side wall 106 of the package
substrate 122, the outer wall 152 of the stiffener 154 is generally
farther from the center of the package substrate 122 than the side
wall 106 of the package substrate. In comparison, the outer wall of
conventional stiffeners are generally the same distance as the side
wall 106 from the center of the package substrate 122. As a result,
the outer wall 152 of the stiffener 154 is generally farther from
the center of the package substrate 122 then outer walls of
conventional stiffeners, thereby providing protection to the side
wall 106 of the package substrate 122 against chipping or other
damage, while providing a larger surface area for handing the chip
package assembly 100 during fabrication.
Bonding of the stiffener 154 to different planes (i.e., the top
surface 102 and side wall 106) of the package substrate 122
increases the stiffness of the package substrate 122 as compared to
conventional chip package assemblies having stiffeners solely
bonded to the top surface of the package substrate. Moreover, the
mounting surfaces 158, 160 provide an increased area for bonding
the stiffener 154, which also increases the robustness of the
stiffener-to-package substrate connection, such as increasing bond
strength and minimizing the propensity for delamination. Still
another advantage is that the side mounting surfaces 160,
interfacing with the side wall 106 of the packing substrate 122,
precisely locates the stiffener 154 on the top surface 102 of the
packing substrate 122, thereby ensuring adequate room for later
fabrication processes and components, while providing an excellent
reference surface for automated fabrication and handling equipment
and processes.
FIG. 2 is a cross sectional schematic view of another integrated
chip package assembly 200 that includes at least one IC die 114 and
stiffener 254 disposed on a package substrate 122. The integrated
chip package assembly 200 is essentially the same as the integrated
chip package assembly 100 depicted in FIG. 1, except that the
stiffener 254 includes a standoff portion 202 extending below a
bottom surface 104 of the package substrate 122.
The standoff portion 202 of the stiffener 254 may be defined as the
portion of the outer wall 152 and side mounting surface 160 of the
stiffener 254 that is disposed below the bottom surface 104 of the
package substrate 122. The standoff portion 202 of the stiffener
254 may extend below the bottom surface 104 of the package
substrate 122 a distance 204 to the bottom surface 162. The
distance 204 may be selected to control the collapse height of the
solder balls 134 disposed inward of the stiffener 254. In one
implementation the distance 204 is selected be about 80 percent of
the pre-collapse height of the solder balls 134. For example,
during reflow, the solder balls 134 collapse during mounting of the
chip package assembly 200 to the PCB 136. During mounting, the
bottom wall 162 of the stiffener 254 contacts the top surface 108
of the PCB 136, thereby controlling the collapse height of the
solder balls 134 to a predefined amount. Another advantage of the
standoff portion 202 is that the standoff portion 202 protects the
solder balls 134 prior to mounting to the PCB 136.
FIG. 3 is a cross sectional schematic view of another integrated
chip package assembly 300 that includes at least one IC die 114 and
stiffener 254 disposed on a package substrate 122. The integrated
chip package assembly 300 is essentially the same as the integrated
chip package assembly 100 depicted in FIG. 1, except that the
stiffener 354 is mounted to both the side wall 106 and the bottom
surface 104 of the package substrate 122.
For example, the side mounting surface 160 of the stiffener 254
contacts and is bonded to the side wall 106 of the package
substrate 122 discussed above, while a top mounting surface 358
contacts and is bonded to the bottom surface 104 of the package
substrate 122. The mounting surfaces 160, 358 may be bonded to the
package substrate 122 utilizing an epoxy or other adhesive as
discussed above.
In one implementation, the inner wall 156 of the stiffener 254 is
advantageously outward of the side wall 106 of the package
substrate 122, maximizing the area of the top surface 102 of the
package substrate 122 available for die mounting or for surface
mounted circuit components. Another advantage of the implementation
depicted in FIG. 3 is that the bottom wall 162 of the stiffener 254
extends below the bottom surface 104 of the package substrate 122,
thereby protecting the solder balls 134 prior to mounting to the
PCB 136.
In the example illustrated in FIG. 3, the stiffener 354 is shown
coupled to the optional lid 150. However, in other examples, the
lid 150 may not be present. In still other examples, the top wall
164 of the stiffener 354 may be flush with, or slightly below the
top surface 108 of the package substrate 122.
FIG. 4 is a cross sectional schematic view of another integrated
chip package assembly 400 that includes at least one IC die 114 and
stiffener 354 disposed on a package substrate 122. The integrated
chip package assembly 400 is essentially the same as the integrated
chip package assembly 400 depicted in FIG. 1, except that the
stiffener 454 includes a standoff portion 202 extending below a
bottom surface 104 of the package substrate 122. In other respects,
the stiffener 454 is essentially the same as the stiffener 354.
In the implementation depicted in FIG. 4, the standoff portion 202
extends a distance 204 below the bottom surface 104 of the package
substrate 122. As discussed above, the distance 204 may be selected
to control the collapse height of the solder balls 134 disposed
inward of the stiffener 254. In one implementation the distance 204
is selected be about 80 percent of the pre-collapse height of the
solder balls 134. Another advantage of the standoff portion 202 is
that the standoff portion 202 protects the solder balls 134 prior
to mounting to the PCB 136.
In the example illustrated in FIG. 4, the stiffener 454 is shown
coupled to the optional lid 150. However, in other examples, the
lid 150 may not be present. In still other examples, the top wall
164 of the stiffener 454 may be flush with, or slightly below the
top surface 108 of the package substrate 122.
FIG. 5 is a partial sectional view of an alternative example of a
stiffener 500 which may be utilized in an integrated chip package
assembly, such as the integrated chip package assemblies 100, 200,
300, 400 of FIGS. 1-4, among others. Optionally, the stiffener 500
may include a standoff portion 202, as shown in FIG. 2 or FIG.
4.
Similar to the other stiffeners described herein, the stiffener 500
includes a top wall 514, a bottom wall 516, an outer wall 512 and
an inner all 510. The inner wall 510 of the stiffener 500 includes
a substrate edge receiving pocket 518 that is configured to capture
the side wall 106 of the package substrate 122. The substrate edge
receiving pocket 518 may be a groove or area between projections
extending from the inner all 510 of the stiffener 500. In the
implementation depicted in FIG. 5, the substrate edge receiving
pocket 518 is defined between two barbs 502, 504 extending from the
inner wall 510 of the stiffener 500. The barbs 502, 504 include an
entrance angle 530 that facilitates the side wall 106 of the
package substrate 122 to be slid and snap-fit into the substrate
edge receiving pocket 518. In some implementations, use of an
adhesive to bond the package substrate 122 into the substrate edge
receiving pocket 518 may be omitted.
FIG. 6 is top view of stiffeners 610 that may be utilized in an
integrated chip package assembly, such as the integrated chip
package assemblies 100, 200, 300, 400 of FIGS. 1-4, among others.
The stiffeners 610 may be secured to the package substrate 122 of
the chip package assembly 100 in any manner as described above, or
other suitable manner.
The stiffeners 610 are disposed along edges of the side walls 106.
Optionally, the stiffeners 610 may extend along edges of the side
walls 106 to engage the corners 602 of the package substrate 122.
The stiffeners 610 may have any of the profiles described above for
the stiffeners 154, 254, 354, 454, 500, or other suitable profile.
Although only one stiffener 610 is shown engaged with every other
side wall 106 of the package substrate 122 in FIG. 6, one or more
stiffeners 610 may be engaged with at least one side wall 106 of
the package substrate 122. For example, one or more stiffeners 610
may be engaged with each of the four side walls 106 of the package
substrate 122.
Additionally, although the stiffeners 610 are shown engaging the
top surface 102 and side walls 106 of the package substrate 122,
the stiffeners 610 may alternatively be engage the bottom surface
104 and side walls 106 of the package substrate 122 as shown in
FIG. 3, or engage the package substrate with a receiving pocket 518
as shown in FIG. 5. Optionally, the stiffeners 610 may include a
standoff portion 202, as shown in FIG. 2 or FIG. 4.
FIG. 7 is top view of stiffeners 710 that may be utilized in an
integrated chip package assembly, such as the integrated chip
package assemblies 100, 200, 300, 400 of FIGS. 1-4, among others.
The stiffeners 710 may be secured to the package substrate 122 of
the chip package assembly 100 in any manner as described above, or
other suitable manner.
The stiffeners 710 are disposed along edges of the side walls 106
and engage at least one corner 602 of the package substrate 122.
The stiffeners 710 may have any of the profiles described above for
the stiffeners 154, 254, 354, 454, 500, 610, or other suitable
profile. Although only two stiffeners 710 are shown circumscribing
the perimeter of the side walls 106 of the package substrate 122 in
FIG. 7, three or more stiffeners 710 may be utilized.
Additionally, although the stiffeners 710 are shown engaging the
top surface 102 and side walls 106 of the package substrate 122,
the stiffeners 710 may alternatively be engage the bottom surface
104 and side walls 106 of the package substrate 122 as shown in
FIG. 3, or engage the package substrate with a receiving pocket 518
as shown in FIG. 5.
FIG. 8 is top view of a stiffener 810 that may be utilized in an
integrated chip package assembly, such as the integrated chip
package assemblies 100, 200, 300, 400 of FIGS. 1-4, among others.
The stiffener 810 may be secured to the package substrate 122 of
the chip package assembly 100 in any manner as described above, or
other suitable manner. Although only a single ring-shaped stiffener
810 is shown circumscribing the perimeter of the side walls 106 of
the package substrate 122 in FIG. 8, multiple stiffeners 810 may be
utilized.
The stiffener 810 is disposed along edges of the side walls 106 and
engages the corners 602 of the package substrate 122. The stiffener
810 generally may have any of the profiles described above for the
stiffeners 154, 254, 354, 454, 500, or other suitable profile.
Additionally, although the stiffener 810 is shown engaging the top
surface 102 and side walls 106 of the package substrate 122, the
stiffener 810 may alternatively be engage the bottom surface 104
and side walls 106 of the package substrate 122 as shown in FIG. 3,
or engage the package substrate with a receiving pocket 518 as
shown in FIG. 5.
In the implementation depicted in FIG. 8, the stiffener 810
includes at least one portion, for example a surface mounting pad
850, that overlays the top surface 102 at least one of the corners
602 of the package substrate 122. Other portions 852 of the
stiffener 810 between the surface mounting pad 850 do overlays the
top surface 102. In the illustrated example, the stiffener 810
includes four mounting pads 850 that overlay the top surface 102 at
each of the corners 602 of the package substrate 122. The surface
mounting pads 850 do not overlay the entire region (i.e., the
portion 852) of the side wall 106 between adjacent corners 602.
As better illustrated in the sectional view of FIG. 9 taken along
section lines 9-9 of FIG. 8, the stiffener 810 includes a side
mounting surface 160 and an outer wall 820. The side mounting
surface 160 is bonded to the side wall 106 of the package substrate
122 as described above. As additionally illustrated in the
sectional view of FIG. 10 taken along section lines 10-10 of FIG.
8, the stiffener 810 includes a bottom mounting surface 158 that is
bonded to the top surface 102 of the package substrate 122 as
described above.
Alternatively, the mounting pads 850 may overlay the bottom surface
104 of the package substrate 122. In such an implementation, the
stiffener 810 is configured to include a top mounting surface 358
that is bonded to the bottom surface 104 of the package substrate
122, as described above with reference to FIG. 3.
FIG. 11 is a top view of a stiffener 1110 that may be utilized in
an integrated chip package assembly, such as the integrated chip
package assemblies 100, 200, 300, 400 of FIGS. 1-4, among others.
The stiffener 1110 is similar to the stiffener 810 describe above,
except that stiffener 1110 includes at least one surface mounting
pad 850 that overlays the top surface 102 between the corners 602
of the package substrate 122. The corners 602 of the package
substrate 122 are generally exposed by the stiffener 1110.
In the illustrated example, the stiffener 1110 includes four
mounting pads 850 that overlay the top surface 102 between each of
the corners 602 of the package substrate 122. The surface mounting
pads 850 of the stiffener 1110 do not overlay the corners 602 of
the package substrate 122. The portion of the stiffener 1110 not
overlaying the top surface 102 is configured as shown in the
sectional view of the stiffener 810 illustrated in FIG. 9. The
portion of the stiffener 1110 overlaying the top surface 102 (i.e.,
the surface mounting pad 850) is configured as shown in the
sectional view of the stiffener 810 illustrated in FIG. 10.
The stiffener 1110 may be secured to the package substrate 122 of
the chip package assembly 100 in any manner as described above, or
other suitable manner. Although only a single ring-shaped stiffener
1110 is shown circumscribing the perimeter of the side walls 106 of
the package substrate 122 in FIG. 11, multiple stiffener 1110 may
be utilized.
The stiffener 1110 is disposed along edges of the side walls 106
and engages the corners 602 of the package substrate 122. The
stiffener 810 generally may have any of the profiles described
above for the stiffeners 154, 254, 354, 454, 500, or other suitable
profile. Additionally, although the stiffener 1110 is shown
engaging the top surface 102 and side walls 106 of the package
substrate 122, the stiffener 1110 may alternatively be engage the
bottom surface 104 and side walls 106 of the package substrate 122
as shown in FIG. 3, or engage the package substrate with a
receiving pocket 518 as shown in FIG. 5.
In the implementation depicted in FIG. 11, the stiffener 1110
includes at least one surface mounting pad 850 that overlays the
top surface 102 between at least two of the corners 602 of the
package substrate 122. In the illustrated example, the stiffener
1110 includes four mounting pads 850 that overlay the top surface
102 between each of the corners 602 of the package substrate 122.
The surface mounting pads 850 do not overlay the corners 602 of the
package substrate 122.
Alternatively, the mounting pads 850 may overlay the bottom surface
104 of the package substrate 122. In such an implementation, the
stiffener 810 is configured to include a top mounting surface 358
that is bonded to the bottom surface 104 of the package substrate
122, as described above with reference to FIG. 3.
FIGS. 12-13 are partial sectional views of a stiffener 154
interfaced with an adapter 1200 or an adapter 1300 that may be
utilized in an integrated chip package assembly, such as the
integrated chip package assemblies 100, 200, 300, 400 of FIGS. 1-4,
among others. Although the adapters 1200, 1300 are illustrated in
FIGS. 12-13 as interfacing with the stiffener 154, the adapters
1200, 1300 may be utilized with the other stiffeners described
herein. For example, the stiffener 154 may include a standoff
portion 202 as shown in FIG. 4.
The adapter 1200 may be fabricated from the same materials as the
stiffener 154. The adapter 1200 is bonded to the stiffener 154 to
increase the rigidity of the package substrate 122. The adapter
1200 may be bonded to the stiffener 154 utilizing any suitable
adhesives, such as the adhesives utilized to bonded the stiffener
154 to the package substrate 122. Alternatively, the adapter 1200
may be mechanically coupled to the stiffener 154. If an optional
lid 150 is incorporated into the chip package assembly, the lid 150
may be bonded to the adapter 1200.
Referring first to the implementation depicted in FIG. 12, the
adapter 1200 includes a top wall 1206, a bottom wall 1210, an inner
wall 1212 and an outer wall 1204. The adapter 1200 also includes an
outer mounting surface 1202 and a bottom mounting surface 1208. At
least one or both of the mounting surfaces 1202, 1208 are bonded to
the adjacent surface of the stiffener 154, thereby increasing the
overall stiffness of the stiffener/adaptor assembly, and
consequently, the increasing the stiffness of the package substrate
122 mounted thereto. The interface between the outer mounting
surface 1202 and the inner wall 156 of the stiffener 154 precisely
locates the adapter 1200 on the stiffener 154.
Referring now to the implementation depicted in FIG. 13, the
adapter 1300 includes a top wall 1306, a bottom wall 1310, an inner
wall 1312 and an outer wall 1304. The adapter 1300 also includes an
inner mounting surface 1302 and a bottom mounting surface 1308. At
least one or both of the mounting surfaces 1302, 1308 are bonded to
the adjacent surface of the stiffener 154, thereby increasing the
overall stiffness of the stiffener/adaptor assembly, and
consequently, the increasing the stiffness of the package substrate
132 mounted thereto. The interface between the inner mounting
surface 1302 and the outer wall 152 of the stiffener 154 precisely
locates the adapter 1300 on the stiffener 154.
The adapters 1200, 1300 allow a standardized stiffener to be
utilized with a predefined package substrate in a large variety of
IC package assembly configurations, with only the simple and
inexpensive adapter needing to be customized for a specific design.
For example, the adapters 1200, 1300 may be utilized with any of
the stiffeners 154, 254, 454, 500, 710, 810, 1110 described above,
with or without lids 150. Use of a standardized stiffener and
package substrate size allows different chip package assemblies to
be fabricated more rapidly with less expense.
FIG. 14 is a block diagram of one example of a method 1400 for
forming a chip package assembly 100 having improved stiffener. The
stiffener may be any of the stiffeners described above, or other
suitable stiffener. The method 1400 begins at block 1402 by
printing surface mounting paste on a substrate, such as the package
substrate 122, at pad locations where surface components are to be
placed. The surface mounting paste may be printed using screen
printing, ink jet printing or other suitable process.
At block 1404, surface components, such as diodes, capacitors,
resistors and the like, are mounted to the surface mounting paste.
At block 1406, a first reflow process is performed to reflow solder
to electrically connect the component leads of the surface
components to the pads on the package substrate 122. The first
reflow process may be performed in a conveyor oven or using other
suitable technique. At block 1408, solder bumps formed on the
package substrate 122 are coined. Package bumps 120 are then formed
on the coined surface.
At block 1410, the stiffener is attached to the package substrate
122. As discussed above, the stiffener may be attached to the side
wall 106 and at least one of the top and bottom surfaces 102, 104
of the package substrate 122 using an epoxy or other suitable
adhesive. At block 1412, IC chips, such as the IC dice 114, are
attached to the package substrate 122. The IC dice 114 may be
directly attached to the package substrate 122, or an interposer
112 already having the IC dice 114 mounted thereon may be attached
to the package substrate 122. As the stiffener is already attached
to the package substrate 122, the package substrate 122 is less
susceptible to warpage and/or bowing during the chip attach process
at block 1412.
At block 1414, a second reflow process is performed to reflow
solder in the package bumps 120 to electrically connect the IC dice
114 to the package substrate 122. The second reflow process may be
performed in a conveyor oven or using other suitable technique. As
the stiffener is already attached to the package substrate 122, the
package substrate 122 is less susceptible to warpage and/or bowing
due to thermal expansion during the second reflow process performed
at block 1414.
At block 1416, underfill, such as the undermolding 144, is
dispensed between the package substrate 122 and interposer 112. If
the IC dice 114 are directly mounted to the package substrate 122,
the underfill may be directly disposed between the IC dice 114 and
the package substrate 122. Optionally, if a lid 150 is utilized,
the lid 150 may be disposed over the IC dice 114 and coupled to the
stiffener after the underfill process is complete at block
1416.
At block 1418, solder balls 134 are attached to a side of the
package substrate 122 opposite the IC dice 114. As the stiffener is
already attached to the package substrate 122, the package
substrate 122 is less susceptible to warpage and/or bowing during
the solder ball attach process performed at block 1418.
At block 1420, a third reflow process is performed to reflow solder
in the solder balls 134 to electrically connect the package
substrate 122 to the PCB 136. The third reflow process may be
performed in a conveyor oven or using other suitable technique. As
the stiffener is already attached to the package substrate 122, the
package substrate 122 is less susceptible to warpage and/or bowing
due to thermal expansion during the third reflow process performed
at block 1420.
FIG. 15 is a block diagram of another example of a method 1500 for
forming a chip package assembly 100 having improved stiffener. The
stiffener may be any of the stiffeners described above, or other
suitable stiffener. The method 1500 begins at block 1410 wherein a
stiffener is attached to a package substrate 122. As discussed
above, the stiffener may be attached to the side wall 106 and at
least one of the top and bottom surfaces 102, 104 of the package
substrate 122 using an epoxy or other suitable adhesive.
At block 1402 by printing surface mounting paste on a substrate,
such as the package substrate 122, at pad locations where surface
components are to be placed. The surface mounting paste may be
printed using screen printing, ink jet printing or other suitable
process. At block 1404, surface components, such as diodes,
capacitors, resistors and the like, are mounted to the surface
mounting paste.
At block 1412, IC chips, such as the IC dice 114, are attached to
the package substrate 122. The IC dice 114 may be directly attached
to the package substrate 122, or an interposer 112 already having
the IC dice 114 mounted thereon may be attached to the package
substrate 122. As the stiffener is already attached to the package
substrate 122, the package substrate 122 is less susceptible to
warpage and/or bowing during the chip attach process at block
1412.
At block 1414, a reflow process is performed to reflow solder in
the package bumps 120 to electrically connect the IC dice 114 to
the package substrate 122. The reflow process may be performed in a
conveyor oven or using other suitable technique. As the stiffener
is already attached to the package substrate 122, the package
substrate 122 is less susceptible to warpage and/or bowing due to
thermal expansion during the reflow process performed at block
1414.
At block 1416, underfill, such as the undermolding 144, is
dispensed between the package substrate 122 and interposer 112. If
the IC dice 114 are directly mounted to the package substrate 122,
the underfill may be directly disposed between the IC dice 114 and
the package substrate 122. Optionally, if a lid 150 is utilized,
the lid 150 may be disposed over the IC dice 114 and coupled to the
stiffener after the underfill process is complete at block
1416.
At block 1418, solder balls 134 are attached to a side of the
package substrate 122 opposite the IC dice 114. As the stiffener is
already attached to the package substrate 122, the package
substrate 122 is less susceptible to warpage and/or bowing during
the solder ball attach process performed at block 1418.
At block 1420, another reflow process is performed to reflow solder
in the solder balls 134 to electrically connect the package
substrate 122 to the PCB 136. The reflow process performed at block
1420 may be performed in a conveyor oven or using other suitable
technique. As the stiffener is already attached to the package
substrate 122, the package substrate 122 is less susceptible to
warpage and/or bowing due to thermal expansion during the reflow
process performed at block 1420.
One advantage of the methods 1400, 1500 is that the stiffener
attach at block 1410 occurs prior to the chip attach at block 1412,
which happens in reverse order when practicing a conventional
fabrication process. Attaching the stiffener prior to the chip
reduces warpage that may be induced during the subsequent solder
reflows. Thus, the methods 1400, 1500 keeps the substrate flat
during chip-attach reflow, ensuring proper C4 joint formation.
Additionally, the flatter chip package assembly 100, imparts less
stress on the C4 solder joints, as compared to conventionally
fabricated chip packages, and thus, helps prevent post-reflow
solder joint defects from occurring.
Thus, a chip package assembly and method for fabricating the same
have been provided which utilize a stiffener to improve the
resistance of a package substrate to out of plane deformation. The
implementations described above advantageously provide one or more
of the following benefits: enhanced warpage control while
maintaining lower package profile; BGA solder ball height collapse
control; stiffener standardization through use of customizable
adaptors; pre-attached stiffeners for enhanced warpage control at
chip-attach reflow; larger stiffeners that provide greater surface
area for clamping during package fabrication; edge protection for
the package substrate during handling and processing; and
mechanical damage protection for BGA solder balls, among other
benefits.
While the foregoing is directed to embodiments of the present
invention, other and further embodiments of the invention may be
devised without departing from the basic scope thereof, and the
scope thereof is determined by the claims that follow.
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